The viruses

Question 1

What type of parasite are viruses

Answer 1

Obligate intracellular parasites

Question 2

Define virion

Answer 2

W virus particle that is extracellular and can move from one cell to another

Question 3

5 methods of studying viruses

Answer 3

Tissue culture 
Physical methods - EM, ultracentifugation
Serology/immunological methods
DNA sequencing
Pathology + transmission studies

Question 4

What viral structure are those that infect prokaryotic cells

Answer 4

Usually have naked capsids

Question 5

What viral structure are those that infect eukaryotic cells

Answer 5

Most often enveloped

Question 6

Viral capsid

Formed form
Packed with

Answer 6

Formed form protein sub units

Packed with viral DNA

Question 7

What do virions have

Answer 7

Molecular receptors that enable recognition and attachment onto host cells

Question 8

What is the envelope covering the capsid of eukaryotic viruses derived from

Answer 8

The host cell

Question 9

Large virus

Answer 9

Mimivirus

Question 10

Baltimore classification

Answer 10

System used to classify viruses based on their manner of mRNA synthesis

Question 11

How many Baltimore groups are there?

Answer 11

7

Question 12

What three things do Baltimore classification take into account?

Answer 12

1. If viral genome is DNA or RNA
2. If viral genome is ss or ds
3. If the sense of a ssRNA is positive or negative

Question 13

Most common Baltimore classification of viruses that infect bacteria and archaea

Answer 13

dsDNA

ssDNA

Question 14

Most common classification of viruses that infect eukaryotic cells

Answer 14

RNA viruses

Question 15

Viral genomes - DNA (5 things)

Answer 15

Reactive - Deoxyribose less reactive due to C-H bonds
Alkaline - DNA stable in alkaline
Grooves - DNA has smaller grooves more resistant to enzymatic attack
Double stranded
Mutation rate - lower

(RAG DM)

Question 16

Viral genomes - RNA (5 things)

Opposite of DNA
RAG DM
But ribose more reactive due to

Answer 16

C-OH bonds

Question 17

How are viruses phylogenetically analysed

Answer 17

Comparing proteins rather than ribosomal RNA because they don’t have ribosomes

Question 18

Oldest group of viruses appear to be

Answer 18

dsRNA

Question 19

Which viruses may have played a role in transition from RNA to DNA world

Answer 19

Retroviruses

Question 20

Why have some RNA viruses evolved DNA genomes

Answer 20

To protect their genomes from cellular ribonucleases

Question 21

Viroids

Answer 21

Small single stranded circular RNAs that don’t have a protein coating (like most viruses).

Question 22

All known viroids are inhabitants of

Answer 22

Angiosperms

Question 23

General bacterial virus life cycle

Answer 23

1. Virions locate cell
2. Replicate in cell
3. Leave the cell

Question 24

Take home message about viruses

Answer 24

There is huge variety in the way they work (entry strategies, specific things about their life cycles, exit strategies)

Question 25

Pseudolysogeny | XXX

Answer 25

Stalled development of a bacteriophage in a host cell No multiplication of phage genome/replication alongside cell cycle of the host

Question 26

Mollicutes

Answer 26

Class of bacteria without a cell wall

Question 27

X

Answer 27

Viruses can infect bacteria Viruses can infect eukaryotic cells The general life cycle is similar in that they enter the cell, replicate then leave But in eukaryotes the entry strategies might be more complex

Question 28

What is segmented RNA viruses

Answer 28

Viruses in which the genome consists of more than one RNA molecule (Genome segments can be packaged into a single virion particle or into separate particles)

Question 29

Disadvantages of segmented RNA viruses

Answer 29

When 2nor more compatible viruses co infect a cell it enables re combination of their genomes which can have consequences on evolution and immune escape

Question 30

How many segments does influenza virus have

Answer 30

8 ssRNA segments

Question 31

What is antigenic shift

Answer 31

Two or more different viral strains or two or more different viruses combine to form a new sub type that has a mixture of the surface antigens of the original strains

Question 32

Where do influenza virus mutations often occur

Answer 32

HA (haemagglutin) genes NA (neuraminidase) genes Which can affect binding or neutralising antibodies from the immune system

Question 33

Why does influenza have pandemic potential

Answer 33

Antigenic shift could occur producing a sudden strain which nobody has immunity against and existing vaccines do not work for

Question 34

How does EBV spread

Answer 34

Orally

Question 35

What type of virus is EBV and what family does it belong to

Answer 35

dsDNA | Herpes family

Question 36

What time of infection does EBV usually form

Answer 36

Latent infection | Persists as an episome of circular DNA within the nuclei of infected B cells

Question 37

How can EBV cause cancer

Answer 37

Mutations in cells infected with EBV can lead to cancerous changes

Question 38

What are endogenous retroviruses

Answer 38

Viral elements in the genome that closely resemble and can be derived from retroviruses

Question 39

What are transposable elements

Answer 39

Sequences of DNA that Juno from one location in the genome to another

Question 40

How are transposable elements classified ?

Answer 40

Transposons and retro elements Retroelements: non LTR or LTR

Question 41

Define LTR

Answer 41

Long terminal repeat | Classification of retroelement

Question 42

In the human genome what % of retro elements make up the 3 million transposable elements

Answer 42

90% transposable elements are retroelements Other 10% are transposons

Question 43

What are retroelements

Answer 43

Endogenous components of eukaryotic genomes that are amble to amplify to new locations in the genome through an RNA intermediate

Question 44

Disadvantage if retroelements

Answer 44

Integration could cause harm by disrupting or dis regulating essential genes

Question 45

Paleovirology

Answer 45

Study of viruses that existed in the past but are now extinct

Question 46

What are EVEs - endogenous viral elements ?

Answer 46

A DNA sequence derived from a virus and present within the germ line of a non viral organism

Question 47

Reticuloendotheliosis virus

Answer 47

Can cause running and tumours in poultry

Question 48

Examples of zoonotic disease

Answer 48

Influenza from birds and pigs to humans SARS from bats to humans

Question 49

What does Ebola virus infect

Answer 49

Macrophages and epithelial cells

Question 50

Example of a virus infecting a virus

Answer 50

APMV large virus in amoeba. Sputnik is a virus that harms APMV replication

Question 51

Summary - viruses are

Answer 51

Obligate cellular parasites Abundant on earth Affect all living things including other viruses

Question 52

Summary - viruses exhibit a wide diversity of

Answer 52

Structures Genome compositions and mutation rates Life cycles

Question 53

Summary - viruses have to

Answer 53

Spread among hosts Enter cells Replicate Leave the host cell/integrate into genome

Question 54

Large proportion of animal genomes are

Answer 54

Of viral origin (have viral sequences in them)